Tuesday, June 26, 2007
Linux vs Windows based web servers - Security
A very good article:
http://www.theregister.co.uk/security/security_report_windows_vs_linux/
It article favours the Linux based server for good security... :)
http://www.theregister.co.uk/security/security_report_windows_vs_linux/
It article favours the Linux based server for good security... :)
Wednesday, October 11, 2006
Pixel size & Resolution
a) The only physically fixed dimensions that a bitmap image has are the number of pixels wide and high in the image (eg 900 x 700 pixels)
b) You can choose to reproduce that bitmap at any physical size, simply according to how large each pixel is made at the time of printing. For example, if each pixel is printed 1/100th of an inch wide, the printed 700 x 900 image would be 7" x 9".
c) Resolution is a measure of how accurately defined an image is, in terms of how many pixels appear in each unit of width or height. The effective resolution in dpi of the final printed image is therefore just the actual width of the printed image divided by the number of pixels shown across that width (ie 100 dpi in the example above).
d) Software may allow you to attach a dpi value to a particular file, or may attach one by default (typically 72 or 96 dpi for a screen oriented application, or 300 dpi for a profession print oriented application). But this number is entirely arbitrary and serves only one purpose - it is to allow the software to represent dimensions in 'real world' units such as inches, rather thna pixels. It does not alter or control the definition of the image itself, merely what dimensions will be shown on the display and, usually, what default printing width will be used.
e) in colour printing there are further issues related to the 'screening' or 'ruling' colour separation processes used to represent colour in print. These are usually measured in lpi (lines per inch) and are not the same as the dpi of the image. As a rule of thumb, for any given screen ruling (typically 100-175 lpi), the source itmap images should be reproduced so as to provide a resolution in dpi at around twice the screen ruling in lpi (typically needing a resolution of 250-300dpi for professional colour work).
b) You can choose to reproduce that bitmap at any physical size, simply according to how large each pixel is made at the time of printing. For example, if each pixel is printed 1/100th of an inch wide, the printed 700 x 900 image would be 7" x 9".
c) Resolution is a measure of how accurately defined an image is, in terms of how many pixels appear in each unit of width or height. The effective resolution in dpi of the final printed image is therefore just the actual width of the printed image divided by the number of pixels shown across that width (ie 100 dpi in the example above).
d) Software may allow you to attach a dpi value to a particular file, or may attach one by default (typically 72 or 96 dpi for a screen oriented application, or 300 dpi for a profession print oriented application). But this number is entirely arbitrary and serves only one purpose - it is to allow the software to represent dimensions in 'real world' units such as inches, rather thna pixels. It does not alter or control the definition of the image itself, merely what dimensions will be shown on the display and, usually, what default printing width will be used.
e) in colour printing there are further issues related to the 'screening' or 'ruling' colour separation processes used to represent colour in print. These are usually measured in lpi (lines per inch) and are not the same as the dpi of the image. As a rule of thumb, for any given screen ruling (typically 100-175 lpi), the source itmap images should be reproduced so as to provide a resolution in dpi at around twice the screen ruling in lpi (typically needing a resolution of 250-300dpi for professional colour work).
